Run a page which contains Java applet, notice that a process called jp2launcher
is running. What does this process do?
It is part of the "Next Generation Java Plugin" (aka plugin2), the module responsible for starting the JVM for Applets or JNLP (WebStart). I think it also used to launch Java FX. I think it is used starting with Vista, on XP the java.exe is called directly.
Basically the process responsible for talking to the Browser and starting the Java VM. In case of Firefox that launcher is started instead of the "plugin-container" you see for other plugins (like Acrobat).